[llvm-dev] Dealing with illegal operand mappings in RegBankSelect

[Quentin Colombet via llvm-dev]

> On Feb 26, 2019, at 4:18 PM, Matt Arsenault <arsenm2 at gmail.com> wrote:
> 
> 
> 
>> On Feb 26, 2019, at 7:01 PM, Quentin Colombet <qcolombet at apple.com <mailto:qcolombet at apple.com>> wrote:
>> 
>> I don’t get what you mean by “applyMapping to deal with it”. Won’t applyMapping will insert copies to rewrite these, hence how is this different from what the repairing code does?
>> Unless, maybe, you’re talking about the target specific RegisterBankInfo::applyMapping not RegBankSelect::applyMapping.
>> 
>> If that’s the case what do you do in here that we could maybe generalize?
>> 
> Sorry, I mean report them as legal so they are left as-is with no copy inserted. I can see the operand is illegal and do everything needed in the target applyMappingImpl (first sample case is https://reviews.llvm.org/D58512 <https://reviews.llvm.org/D58512>)

Wow, that’s quite a lot of code to fix a couple of operands :)

Couldn’t we do that expansion as part of the selection of the “pseudo copy”?

> 
> -Matt

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